Pablo Sandoval homered off Richard to back Madison Bumgarner's fourth straight victory, and the Giants beat the Padres 4-1 on Sunday to deny San Diego its first series win of the season.

It's hard to imagine now, but Bumgarner lost his first six starts of 2011 - winning his first game May 19 and his fourth on June 26.

``It's obvious we think a lot of Madison and what he's done since he got up here, and he's just going to get better and better,' Giants manager Bruce Bochy said. ``For a kid his age, it's impressive to see how he throws the ball. I'm not surprised to see what he's done the first month.'

Joaquin Arias added a two-run triple in the sixth inning to turn a one-run lead into 4-1 - one of a few at_bats Richard would like to have back.

The Giants wasted no time giving Bumgarner (4-1) a lead against Richard (1-3), a day after Anthony Bass retired the first 17 San Francisco batters before pitcher Tim Lincecum broke up the no-hit bid with an infield single with two outs in the sixth.

Bumgarner struck out a season-best six in 7 2-3 innings for his team-leading fourth victory, and he has won four straight starts since losing his season debut at Arizona. He owns a 1.61 ERA during the winning streak. Bumgarner allowed six hits and walked one.

``I think that a pitcher's record is a little bit overrated. There are so many factors that you can't control that go into it,' Bumgarner said. ``But it's nice to have a lot of wins.'

Angel Pagan led off the first with a single, then Richard threw wildly past first on a pickoff attempt for a two-base error as the ball went to the visiting bullpen. Melky Cabrera followed with a sacrifice fly before Sandoval connected for his fourth home run after his season-opening 20-game hitting streak ended in Saturday night's 2-1 win.

The Padres scored in the fifth on Chris Denorfia's double that was misread in center field by Pagan, who took a step in before having to backpedal for a ball that traveled further than he anticipated. That scored Jason Bartlett, who got aboard on a leadoff single.

Bumgarner, who earlier this month received a $35.56 million, six-year contract that runs through 2017, struck out 13 San Diego batters in his last start against the Padres on Sept. 5, 2011. He had them guessing again this time.

``It was a well-pitched game by Richard. He kept the ball down and got his groundballs,' San Diego manager Bud Black said. ``Bumgarner threw a good game. Look at the results. Once he got into the middle part of the game he used his slider, his breaking ball, for strikes.'

The 22-year-old left-hander - second-youngest on the team behind rookie catcher Hector Sanchez - has held opponents to two or fewer runs in his last nine starts at AT&T Park. Bumgarner also has won 13 of his last 18 decisions since July 14, 2011.

``I have a hard time believing however old he is - 22?' teammate Brett Pill said.

Sergio Romo retired one batter in the eighth and Santiago Casilla allowed a two-out walk to Cameron Maybin in the ninth but finished for his fourth save in four chances.

Pill singled and doubled off Richard, who lost his third straight start. He gave up four runs and eight hits in seven innings.

When Buster Posey drew a walk in the sixth, it ended a stretch of 26 innings and 104 batters faced by the Padres without a walk since Wilson Ramos received a free pass on Thursday. According to STATS LLC, it was the team's longest such streak since San Diego pitchers went 29 innings without a walk from May 12-15, 2007.

``Posey's at-bat, the walk, hurt us. If we get him to put the ball in play it could have been different,' Richard said. ``The odds are in your favor when you get the guy to put the ball in play. When you give them a free pass, it doesn't usually go your way.'

Richard had allowed three or fewer earned runs in his previous seven starts against the Giants dating to April 19, 2010.

San Diego has lost six series and split a four-gamer with the Phillies so far this season.

NOTES: Orlando Hudson had the day off after going 0 for 4 on Saturday to have his 10-game hitting streak snapped - longest by a Padres player in 2012. Andy Parrino started at 2B in his place. ... Padres RHP Tim Stauffer, who began the season on the 15-day disabled list with a strained elbow, began a rehab assignment with Class-A Lake Elsinore and pitched 3 2-3 innings. He allowed six hits, two earned runs, struck out seven and didn't have a walk. Black said he'll make another start in the minors. ... Richard's final 2011 start came vs. San Francisco before he had season-ending left shoulder surgery.